1. Field of the Invention
The present invention relates to a throttle-opening detecting apparatus which detects the rotation angle of a throttle grip mounted on a handle bar used in a vehicle such as a two-wheeled vehicle to thereby detect the throttle-opening.
2. Description of the Related Art
A throttle-opening detecting apparatus for use in a two-wheeled vehicle is structured such that it detects the rotation angle of a throttle grip mounted on a handle bar and transmits its detect signal to an electronic control unit carried on board the two-wheeled vehicle; and, in accordance with the detect signal, the electronic control unit executes a given operation and, based on the operation result of the electronic control unit, the ignition timing of an engine as well as the opening and closing of an exhaust valve can be controlled.
Conventionally, a throttle-opening detecting apparatus, for example, as disclosed in JP-A-4-254278, comprises mainly a drive pulley worked with a throttle grip and rotatable in the same direction as the throttle grip, a drive gear disposed in the lower portion of the drive pulley, a detecting gear rotatable in meshing engagement with the drive gear, and a potentiometer for detecting the rotation angle of the detecting gear; and, these drive pulley, drive gear, detecting gear and potentiometer are respectively incorporated in a case which is fixed to the handle bar.
According to the above structure, in case where the throttle grip is rotated, the drive pulley is worked with the rotative direction of the throttle grip and, at the same time, the detecting gear in meshing engagement with the drive gear disposed in the lower portion of the drive pulley is also rotated. The rotation angle of the detecting gear is detected by the potentiometer to thereby detect the rotation angle of the throttle grip, that is, the throttle-opening. Such rotation of the detecting gear is executed about an axis extending substantially in parallel to the extension direction of the handle bar, and the angle of such rotation is detected by the potentiometer.
However, in the above-mentioned conventional throttle-opening detecting apparatus, since the rotation of the detecting gear is executed about an axis extending substantially in parallel to the extension direction of the handle bar, in order to allow the shifting motion of the detecting gear caused by the rotational movement of the detecting gear, the case must be increased in thickness. That is, in order to prevent the detecting gear from interfering with the case while the detecting gear is rotating, the dimension of the case in the direction where it is expanded from the handle bar must be set large, which unfavorably results in the large-sized outer shape of the throttle-opening detecting apparatus.